Javascript replace syntax

Javascript replace syntax DEFAULT

Javascript String replace: How to replace String in JavaScript

Javascript replace() method does not change the calling String object. It simply returns a new string. To perform a global search and replace, including the g switch in the regular expression. Replacing text in a string is a general operation and effortless operation.

Javascript String replace()

The String replace() is a built-in JavaScript function thatsearches the string for a specified value or keyword or a regular expression and returns the new string where the specified values are replaced. The pattern can be a String or the RegExp, and the replacement can be the string or a method to be called for each match.

Syntax

The syntax for the Javascript String replace() function is the following.

string.replace(searchvalue, newvalue)

Parameters

The replace() function takes two parameters.

The searchvalue is a required parameter, and it is the value or regular expression that the new value will replace.

The newvalue is a required parameter, and it is the value to replace the search value with.

Return Value

The replace() method returns the new string, with some matches of a pattern replaced by a replacement.

Example

Now let us take an example.

let myStr = 'Bill is the richest person alive'; console.log(myStr.replace('Bill', 'Jeff'));

The replace() method does not change a String object itself; it is called upon. It just returns a new string.

See another code example.

// app.js let myStr = 'Apple TV will be launching on 1st November '; console.log(myStr.replace('Apple TV', 'Apple TV+'));

See the output.

➜ es git:(master) ✗ node app Apple TV+ will be launching on 1st November ➜ es git:(master) ✗

Javascript String replace() method does not change the String object it is called on. It simply returns the new string. For example, perform a global search and replace, including the g switch in the regular expression.

Javascript string replace with regexp match.

Matching an exact substring is good, but often we find ourselves needing to match a pattern instead. It can quickly be done by using the regular expression as the first argument.

// server.js let myStr = 'we can do whatever we want, we are venom'; myStr = myStr.replace(/w/g, 'b'); console.log(myStr);

You can check it via the node server. Just go to the terminal and go to the root of the above server.js file and type the following command.

node server

See the output.

➜ es git:(master) ✗ node app be can do bhatever be bant, be are venom ➜ es git:(master) ✗

Specifying a function as a parameter

You can specify a method as the second parameter. In this case, the method will be invoked after the match has been performed. The function’s result (return value) will be used as the replacement string. See the below code.

const replacer = (match, a1, a2, a3, offset, string) => { return [a1, a2, a3].join(' - '); } let newString = 'ABC$*%#'.replace(/([^\d]*)(\d*)([^\w]*)/, replacer); console.log(newString);

Output

ABC - - $*%#

In this example, we have differentiated three types of values with a hyphen and then join the string. Those three types of values are non-digits, non-alphabet, and special characters.

You can see that we have defined a replace() function as a second parameter which will be invoked after the match is performed. Thus, we have completely transformed the original string using the string replace() and join() method.

One thing to note here is that the method will be invoked multiple times for each full match to be replaced if the regular expression in the first parameter is global.

Switching words in a string

To switch a text in Javascript, we can use replace() method because the script uses the capturing groups and the $1 and $2 replacement patterns.

let re = /(\w+)\s(\w+)/; let str = 'Magnus Carlsen'; let newstr = str.replace(re, '$2, $1'); console.log(newstr);

Output

Carlsen, Magnus

You can see that we have switched the string from Magnus Carlsen to Carlsen, Magnus.

Replacing multiple occurrences in JavaScript

If we do not want to use the RegExp, we can use the following technique to replace the substring with multiple occurrences.

// app.js let myStr = 'we can do whatever we want, we are venom'; String.prototype.replaceAll = function(search, replacement) { var target = this; return target.split(search).join(replacement); }; console.log(myStr.replaceAll('w', 'b'));

So that is how we can replace the multiple occurrences. See the output.

➜ es git:(master) ✗ node app be can do bhatever be bant, be are venom ➜ es git:(master) ✗

Replacing an Array of Strings in Javascript

Here is an example where we can iterate over an array of strings and replace the substrings.

let ingredients = ['Y-MEN', 'Avengers', 'Loki']; ingredients = ingredients.map(ingredient => { return ingredient.replace('Avengers', 'Revengers'); }); console.log(ingredients); //[ 'Y-MEN', 'Revengers', 'Loki' ]

See the output.

➜ es git:(master) ✗ node app [ 'Y-MEN', 'Revengers', 'Loki' ] ➜ es git:(master) ✗

Specifying a string as a parameter

Javascript String replace() can include the following particular replacement patterns:

PatternInserts
$$Inserts a “$”.
$&Inserts a matched substring.
$`Inserts a portion of the string that precedes the matched substring.
$’Inserts a portion of the string that follows the matched substring.
$nWhere n is the positive integer less than , inserts the nth parenthesized the submatch string, provided the first argument was a regex object. Note that this is 1-indexed.

Specifying a function as a parameter

We can define the function as a second parameter. In this case, the function will be invoked after the match has been performed. The function returns a result, and that result will be used as the replacement string. On the replace() function, we can also pass the second argument as a function and not the plain string. Let us see how we can use that.

let myStr = '13 million possibilities has been seen by Doctor Strange'; myStr = myStr.replace(/\d+/, (match) => { return +match + 1; }); console.log(myStr);

See the output.

➜ es git:(master) ✗ node app 14 million possibilities has been seen by Doctor Strange ➜ es git:(master) ✗

Replacing multiple strings in Javascript

If you want to replace multiple words in the string with numerous other words, you can use the javascript replace() function.

// app.js let str = "Netflix has StrangerThings, BlackMirror, and HouseOfCards"; let mapObj = { StrangerThings:"Millie Bobby Brown", BlackMirror:"Anthony Mackie", HouseOfCards:"Kevin Spacey" }; replacedString = str.replace(/StrangerThings|BlackMirror|HouseOfCards/gi, function(matched){ return mapObj[matched]; }); console.log(replacedString);

See the output.

➜ es git:(master) ✗ node app Netflix has Millie Bobby Brown, Anthony Mackie, and Kevin Spacey ➜ es git:(master) ✗

If you want to make a reusable code, then you can use the following code snippet.

// app.js function replaceAll(str, mapObj){ let result = new RegExp(Object.keys(mapObj).join("|"),"gi"); return str.replace(result, function(matched){ return mapObj[matched]; }); } let str = "Netflix has StrangerThings, BlackMirror, and HouseOfCards"; let mapObj = { StrangerThings:"Millie Bobby Brown", BlackMirror:"Anthony Mackie", HouseOfCards:"Kevin Spacey" }; replacedString = replaceAll(str, mapObj); console.log(replacedString);

So in the above code, you could pass the str and mapobj to a function, and it would return the transformed string.

It will give us the same output.

Replacing all spaces

Let’s assume that I have a string that contains multiple spaces. I want to replace these with a hash symbol. How can I replace all spaces?

Well, we can use the Javascript split() and Javascript join() methods.

// app.js let str = 'Millie Bobby Brown'; let replaced = str.split(' ').join('#'); console.log(replaced)

See the output.

➜ es git:(master) ✗ node app Millie#Bobby#Brown ➜ es git:(master) ✗

Here is one thing to note is that the above solution is slower on large replacement compared to the reg expression version.

You can use the RegExp on the above code, like the following.

// app.js let str = 'Millie Bobby Brown'; let replaced = str.replace(/\s/g, "#"); console.log(replaced)

You will get the same output.

Conclusion

So in this Javascript String replace() method article, we have seen Javascript replace() function, Javascript replace with regex match, replace an array of strings and all strings, replace characters of the string, replace all spaces with and without regexp.

Finally, Javascript String replace() example is over. Thanks for taking it.

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Sours: https://appdividend.com//09/05/javascript-string-replace-example-tutorial/

JavaScript string.replace() Method

Below is the example of the string.replace() Method. 
 

javascript

 

GfG

The string.replace() is an inbuilt method in JavaScript which is used to replace a part of the given string with some another string or a regular expression. The original string will remain unchanged.
Syntax: 
 

str.replace(A, B)

Parameters: Here the parameter A is regular expression and B is a string which will replace the content of the given string. 
Return Values: It returns a new string with replaced items.
JavaScript code to show the working of this method: 
Code #1: 
Here the contents of the string GeeksForGeeks will be replaced with gfg. 
 

javascript

 

 

 

 

Output: 
 

gfg is a CS portal

Code #2: 
 



javascript

 

 

 

 

 

Output: 
 

gfg is a CS portal

Supported Browsers: 
 

  • Google Chrome 1 and above
  • Edge 12 and above
  • Firefox 1 and above
  • Internet Explorer and above
  • Opera 4 and above
  • Safari 1 and above

 

Hey geek! The constant emerging technologies in the world of web development always keeps the excitement for this subject through the roof. But before you tackle the big projects, we suggest you start by learning the basics. Kickstart your web development journey by learning JS concepts with ourJavaScript Course. Now at it&#;s lowest price ever!




Sours: https://www.geeksforgeeks.org/javascript-string-replace-method/
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How to replace all occurrences of a string in JavaScript

Update:

It's somewhat late for an update, but since I just stumbled on this question, and noticed that my previous answer is not one I'm happy with. Since the question involved replaceing a single word, it's incredible nobody thought of using word boundaries ()

This is a simple regex that avoids replacing parts of words in most cases. However, a dash is still considered a word boundary. So conditionals can be used in this case to avoid replacing strings like :


basically, this question is the same as the question here: Javascript replace " ' " with " '' "

@Mike, check the answer I gave there regexp isn't the only way to replace multiple occurrences of a subsrting, far from it. Think flexible, think split!

Alternatively, to prevent replacing word parts -which the approved answer will do, too! You can get around this issue using regular expressions that are, I admit, somewhat more complex and as an upshot of that, a tad slower, too:

The output is the same as the accepted answer, however, using the /cat/g expression on this string:

Oops indeed, this probably isn't what you want. What is, then? IMHO, a regex that only replaces 'cat' conditionally. (ie not part of a word), like so:

My guess is, this meets your needs. It's not fullproof, of course, but it should be enough to get you started. I'd recommend reading some more on these pages. This'll prove useful in perfecting this expression to meet your specific needs.

http://www.javascriptkit.com/jsref/regexp.shtml

http://www.regular-expressions.info


Final addition:

Given that this question still gets a lot of views, I thought I might add an example of used with a callback function. In this case, it dramatically simplifies the expression and provides even more flexibility, like replacing with correct capitalisation or replacing both and in one go:

Sours: https://stackoverflow.com/questions//how-to-replace-all-occurrences-of-a-string-in-javascript
Replace no Javascript com exemplo Prático

JavaScript - How to Use the String.prototype replace Method in JavaScript

Home   >   Tutorials   >   JavaScript   >   How to Use the String.prototype replace Method in JavaScript

The replace() method operates on a String, returning a new string with the specified changes.

Note: JavaScript strings are immutable. This means that a new string is created in memory for the return value of replace().

Syntax

The syntax of replace() is as follows:

const newStr = str.replace(pattern, newValue)

  • pattern: The pattern to replace. This can be either a String or a regular expression.

If the pattern is a String, only the first matching portion of the string is replaced &#; other instances of the pattern in the string will not be affected.

  • newValue: The value to replace the specified pattern with. This can be either a String or a function.

When newValue is a function, it will be invoked for each match in the string (see the relevant section below).

String.prototype.replace() Examples

Below are a few examples that demonstrate the functionality of the String.prototype.replace() method. The first example below demonstrates the most basic usage of the method:

const str = 'Hello my name is Don and I am a web developer'; const res = str.replace('web', 'software'); console.log(res); // Expected output: Hello my name is Don and I am a software developer

In the example above, the word ‘web’ is the pattern to be replaced. ‘software’ is the newValue. The replace() method finds the first instance of the pattern (web) in the source string, and replaces it with the newValue parameter (software). The end result is that “web” is replaced with “software” in the string, resulting in a new string: “Hello my name is Don and I am a software developer”.

It is not necessary to limit your replace pattern argument to words alone &#; any pattern can be replaced:

const mess = str.replace('am', 'ain\'t'); console.log(mess); // Expected output: Hello my nain'te is Don and I am a web developer

This example results in a string that is a bit messy, and also highlights the limitation of using a string pattern to specify the characters to replace. As the pattern we passed in (am) is a String, only the first instance of the pattern is replaced &#; this first instance is found in the word name.

Note: The backslash (\) character in the code enables us to use special characters in our strings. Without it, the above code would produce a Syntax Error as the single quote after the “n” would otherwise indicate the end of the input string. In this case, the remaining “t” at the end of the string would have no meaning in JavaScript, resulting in the error being thrown.

The above example, because it used a string, only replaced the first instance of the pattern found. To instead change all of the matching patterns, you must use a regular expression (RegEx).

In short, regular expressions are objects which can be used to detect patterns in string input:

const stillAMess = str.replace(/am/g, 'ain\'t'); console.log(stillAMess); // Expected output: Hello my nain'te is Don and I ain't a web developer

In the example above, the pattern parameter receives a RegEx as its value. The RegEx is specified using two slashes (/) surrounding the desired search pattern (am). The final character in the pattern (“g”) occurs after the closing slash of the RegEx and is a flag indicating that the RegEx pattern should be used to perform a global search of the string, resulting in matching multiple instances of the provided pattern.

Note:RegExes are widely used by developers. If you are not familiar with RegExes, you should review them by reading the information at this link.

While the above call to replace() catches all the instances of the desired pattern (am), the result is still not particularly readable. This is due to the search pattern searching for instances of am wherever they are found, instead of replacing only the word form of the pattern as we may have originally desired. We can solve this by adding a space to our search pattern, either before the “a” character or after the “m” character. This will limit our search to only versions of the pattern that have a leading or trailing space, giving us the change we are looking for.

Note: Make sure to add a space in the corresponding location of the newValue argument, or else the replace() method will replace the corresponding space as well.

const correct = str.replace(/am /g, 'ain\'t '); console.log(correct); // Expected output: Hello my name is Don and I ain't a web developer

In the above example, a space was added after the “m” character, as well as after the “t” character in the newValue parameter. This results in the word “am” being replaced by the word “ain’t” in the return value.

How to use a function for the newValue parameter

Let’s demonstrate using a function as the newValue parameter by implementing a very simple encryption mechanism. The following code will take each letter in the const str and replace it with a different character or special character using the characters’ Unicode codes:

const str = 'Hello my name is Don and I am a web developer'; const encrypt = str.replace(/[a-zA-Z]/g, function (char) { let i = char.charCodeAt() + 5; return String.fromCharCode(i); }) console.log(encrypt); // Expected output: Mjqqt r~ sfrj nx Its fsi N fr f |jg ij{jqtujw

In the above example, the pattern parameter received a RegEx argument, telling the replace() method to search for any character in the range a to z, whether the character is lowercase or uppercase. The “g” is again used to indicate a global search; without it, only the first character of the original string will be replaced.

The newValue parameter received a function which does the following:

For every character in the string, let i is declared and assigned the value of the character’s Unicode code value + 5 (note &#; this is a numeric value). The character’s Unicode value is retrieved using the charCodeAt() method.

The function returns a character using the calculated value with the fromCharCode() method, which converts an integer Unicode value (or any other number of significance) into its corresponding character. This value is then returned from the function, replacing the original character in the source string.

To explore this further, let’s look at what happens to the first character in the string &#; “H”:

console.log('H'.charCodeAt()); //Expected output: 72 console.log(String.fromCharCode(77)); //Expected output: M console.log('M'.charCodeAt()); //Expected output: 77

In the example above, we start by retrieving the value of the first letter in const str &#; “H”. The value of “H” in Unicode is By adding 5 to this value, we get the new Unicode value of When this value is provided to fromCharCode(), that function returns the Unicode character with a code value of 77 &#; in this case, the letter “M”.

 

Related Articles

JavaScript &#; How to Replace a Whole String

JavaScript &#; How to Change The Page URL

JavaScript &#; How to Use the toLowerCase() Method

Sours: https://www.tabnine.com/academy/javascript/how-to-use-the-string-prototype-replace-method-in-javascript/

Replace syntax javascript

String.prototype.replace()

The method returns a new string with some or all matches of a replaced by a . The can be a string or a , and the can be a string or a function to be called for each match. If  is a string, only the first occurrence will be replaced.

The original string is left unchanged.

Syntax

Parameters

(pattern)

A object or literal. The match or matches are replaced with or the value returned by the specified .

A that is to be replaced by . It is treated as a literal string and is not interpreted as a regular expression. Only the first occurrence will be replaced.

(replacement)

The that replaces the substring specified by the specified or parameter. A number of special replacement patterns are supported; see the "Specifying a string as a parameter" section below.

If is an empty string, then the substring given by , or the matches for , are removed (rather then being replaced).

(replacement)

A function to be invoked to create the new substring to be used to replace the matches to the given or . The arguments supplied to this function are described in the "Specifying a function as a parameter" section below.

Return value

A new string, with some or all matches of a pattern replaced by a replacement.

Description

This method does not change the calling object. It returns a new string.

To perform a global search and replace, include the switch in the regular expression.

Specifying a string as a parameter

The replacement string can include the following special replacement patterns:

PatternInserts
Inserts a .
Inserts the matched substring.
Inserts the portion of the string that precedes the matched substring.
Inserts the portion of the string that follows the matched substring.
Where is a positive integer less than , inserts the th parenthesized submatch string, provided the first argument was a object. Note that this is -indexed. If a group is not present (e.g., if group is 3), it will be replaced as a literal (e.g., ).
Where is a capturing group name. If the group is not in the match, or not in the regular expression, or if a string was passed as the first argument to instead of a regular expression, this resolves to a literal (e.g., ). Only available in browser versions supporting named capturing groups.

Specifying a function as a parameter

You can specify a function as the second parameter. In this case, the function will be invoked after the match has been performed. The function's result (return value) will be used as the replacement string. (Note: The above-mentioned special replacement patterns do not apply in this case.)

Note that the function will be invoked multiple times for each full match to be replaced if the regular expression in the first parameter is global.

The arguments to the function are as follows:

Possible nameSupplied value
The matched substring. (Corresponds to above.)
The nth string found by a parenthesized capture group (including named capturing groups), provided the first argument to was a object. (Corresponds to , , etc. above.) For example, if , was given, is the match for , and  for .
The offset of the matched substring within the whole string being examined. (For example, if the whole string was , and the matched substring was , then this argument will be .)
The whole string being examined.
In browser versions supporting named capturing groups, will be an object whose keys are the used group names, and whose values are the matched portions ( if not matched).

(The exact number of arguments depends on whether the first argument is a object—and, if so, how many parenthesized submatches it specifies.)

The following example will set to :

Examples

Defining the regular expression in replace()

In the following example, the regular expression is defined in and includes the ignore case flag.

This logs .

Note: See this guide for more explanations about regular expressions.

Using global and ignore with replace()

Global replace can only be done with a regular expression. In the following example, the regular expression includes the global and ignore case flags which permits to replace each occurrence of in the string with .

This logs .

Switching words in a string

The following script switches the words in the string. For the replacement text, the script uses capturing groups and the and replacement patterns.

This logs .

Using an inline function that modifies the matched characters

In this example, all occurrences of capital letters in the string are converted to lower case, and a hyphen is inserted just before the match location. The important thing here is that additional operations are needed on the matched item before it is given back as a replacement.

The replacement function accepts the matched snippet as its parameter, and uses it to transform the case and concatenate the hyphen before returning.

Given , this returns .

Because we want to further transform the result of the match before the final substitution is made, we must use a function. This forces the evaluation of the match prior to the method. If we had tried to do this using the match without a function, the would have no effect.

This is because would first be evaluated as a string literal (resulting in the same ) before using the characters as a pattern.

Replacing a Fahrenheit degree with its Celsius equivalent

The following example replaces a Fahrenheit degree with its equivalent Celsius degree. The Fahrenheit degree should be a number ending with . The function returns the Celsius number ending with . For example, if the input number is , the function returns . If the number is , the function returns .

The regular expression checks for any number that ends with . The number of Fahrenheit degree is accessible to the function through its second parameter, . The function sets the Celsius number based on the Fahrenheit degree passed in a string to the function. then returns the Celsius number. This function approximates Perl's flag.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

Sours: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace
JavaScript Problem: Replace All Occurrences of a String

JavaScript: String replace() method

Example

Let's take a look at an example of how to use the replace() method in JavaScript.

String as the Search Expression

The simplest way to use the replace() method is to find and replace one string with another string. This method does not involve regular expression objects.

For example:

In this example, we have declared a variable called totn_string that is assigned the string value of 'TechOnTheNet is great'. We have then invoked the replace() method of the totn_string to find and replace the first occurrence or match.

We have written the output of the replace() method to the web browser console log, for demonstration purposes, to show what the replace() method returns.

The following will be output to the web browser console log:

TechOnTheNet is the best

In this example, the replace() method performs a search for the first occurrence of the string 'great' and replaces it with the string 'the best'. As you can see, the replace() method returned the string 'TechOnTheNet is the best'.

Regular Expression as the Search Expression (Single Match)

Next, we'll take a look at regular expressions. You can use the replace() method to search for and replace the first occurrence (ie: single match) of a regular expression pattern.

For example:

The following will be output to the web browser console log:

Ye Want to Replace the First Uppercase Character

In this example, the replace() method performs a search for the first occurrence of an uppercase character and replaces that character with 'Y'. The replace() method returns the new string 'Ye Want to Replace the First Uppercase Character' where the 'W' was replaced with 'Y'.

Regular Expression as the Search Expression (Global Match)

You can also use the replace() method to search for all matches of a regular expression pattern. This is done by performing a global match as specified by the g attribute.

For example:

The following will be output to the web browser console log:

Ye Yant to Yeplace all Yppercase Yharacters

In this example, the replace() method performed a global match and searched for all occurrences of uppercase characters and replaced them with 'Y'. This was done by specifying the g attribute at the end of the regular expression.

This time the replace() returned the new string 'Ye Yant to Yeplace all Yppercase Yharacters'.

Sours: https://www.techonthenet.com/js/string_replace.php

You will also like:

JavaScript String - replace() Method



Description

This method finds a match between a regular expression and a string, and replaces the matched substring with a new substring.

The replacement string can include the following special replacement patterns −

PatternInserts
$$Inserts a "$".
$&Inserts the matched substring.
$`Inserts the portion of the string that precedes the matched substring.
$'Inserts the portion of the string that follows the matched substring.
$n or $nnWhere n or nn are decimal digits, inserts the nth parenthesized submatch string, provided the first argument was a RegExp object.

Syntax

The syntax to use the replace() method is as follows −

string.replace(regexp/substr, newSubStr/function[, flags]);

Argument Details

  • regexpA RegExp object. The match is replaced by the return value of parameter #2.

  • substr − A String that is to be replaced by newSubStr.

  • newSubStr − The String that replaces the substring received from parameter #1.

  • function − A function to be invoked to create the new substring.

  • flags − A String containing any combination of the RegExp flags: g - global match, i - ignore case, m - match over multiple lines. This parameter is only used if the first parameter is a string.

Return Value

It simply returns a new changed string.

Example

Try the following example.

Live Demo

<html> <head> <title>JavaScript String replace() Method</title> </head> <body> <script type = "text/javascript"> var re = /apples/gi; var str = "Apples are round, and apples are juicy."; var newstr = str.replace(re, "oranges"); document.write(newstr ); </script> </body> </html>

Output

oranges are round, and oranges are juicy.

Example

Try the following example; it shows how to switch words in a string.

Live Demo

<html> <head> <title>JavaScript String replace() Method</title> </head> <body> <script type = "text/javascript"> var re = /(\w+)\s(\w+)/; var str = "zara ali"; var newstr = str.replace(re, "$2, $1"); document.write(newstr); </script> </body> </html>

Output

ali, zara

javascript_strings_object.htm

Sours: https://www.tutorialspoint.com/javascript/string_replace.htm


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